Conbextra HF: High Flow Cementitious Precision Grout

Product Overview

Conbextra HF is a highly fluid, dual shrinkage compensated, cementitious non-shrink grout supplied as a ready-to-use dry powder. It is specifically engineered to deliver maximum flow properties and extended flow retention times, making it an ideal choice for demanding precision grouting applications.

Key Product Features

Composition and Form

Conbextra HF is formulated as a blend of Portland cements, graded fillers, and chemical additives that impart controlled expansion in both plastic and hardened states. The product is supplied in 20kg moisture-resistant plastic bags and has a shelf life of 36 months under proper storage conditions.

Gap Thickness Range

The product is designed for gap thicknesses ranging from 10mm to 125mm, providing versatility across various installation scenarios. The maximum aggregate size for pumping applications is 2.5mm.

Primary Applications

Conbextra HF is used in a wide range of critical installations, including:

• Critical machine base plates, sole plates, and columns requiring precision placement
• Pumped grouting applications for large volumes
• Grouting applications where pouring access is restricted, benefiting from its excellent flow characteristics
• Free flow precision grouting in various industrial and structural settings
• Underplate grouting applications where expansion properties are essential

Key Advantages

Conbextra HF delivers several significant performance benefits:

• Excellent initial flow and flow retention – Suitable for both pumping and pouring applications
• Rapid strength gain – Facilitates efficient installation and operation of plant and equipment
• High ultimate strength and low permeability – Ensures durability of the hardened grout
• Hydrogen-free gaseous expansion – Provides reliable, predictable expansion characteristics
• Chloride free – Prevents corrosion of embedded metals and reinforcement
• RCS (Respirable Crystalline Silica) Hazard Free – Classified not hazardous for RCS; contains <0.1% RCS
• Non-shrink – Complies with ASTM C1107:2020 standard specifications

Technical Specifications

Consistency Options and Water Requirements

Conbextra HF can be mixed to achieve different consistency levels depending on application requirements:

Consistency	Water Addition (L/20kg bag)	Yield (L mixed material)
Stiff	2.6–3.4	Variable
Plastic	3.4–3.6	Variable
Flowable	3.6–3.8	Variable
Fluid	3.8–4.0	Variable

Compressive Strength Properties

Testing according to AS 1478.2:2005 shows the following compressive strength values across different consistencies:

Consistency	1 Day (MPa)	7 Days (MPa)	28 Days (MPa)
Stiff	50	68	77
Plastic	38	53	64
Flowable	31	48	62
Fluid	27	46	60

Testing according to ASTM C109:2020b (at 3.6L water per 20kg bag) shows:

• 1 Day: 29.8 N/mm²
• 3 Days: 47.5 N/mm²
• 7 Days: 58.6 N/mm²
• 28 Days: 65.8 N/mm²

Flexural and Tensile Strength

• Flexural Strength: 3.2 MPa (1 day), 9.5 MPa (7 days), 10.0 MPa (28 days)
• Indirect Tensile Strength: 2.5 MPa (1 day), 4.5 MPa (7 days), 4.7 MPa (28 days)

Setting Time

• Initial Set: 5.5 hours
• Final Set: 7.5 hours
• (Testing per AS 1012.18:1996; ASTM C953:2017 results: 300–320 minutes)

Fresh Properties

• Fresh Wet Density: 2200 kg/m³ (depending on consistency used)
• Flow Characteristics: 19–25 seconds (Flow Cone per AS 1478.2:2005)
• Flow Characteristics (ASTM): >145% (ASTM C939:2016a)

Standards Compliance

Conbextra HF complies with the following standards:

• AS 1478.2-2005 Appendix E (Early Volume Change)
• AS 1478.2-2005 Table 4.1.2.2 (Consistency)
• ASTM C1107:2020 – Non-shrink specification
• Rapid Mortar Bar Test (RTA T363) – Non-reactive for alkali-reactive particles

Flow Characteristics Guide

The flow distances provided below (in mm) serve as guidelines for different gap depths and hydrostatic head conditions. Actual flow distances will vary depending on site conditions:

Gap Depth (mm)	Flowable 100mm head (mm)	Flowable 250mm head (mm)	Fluid 100mm head (mm)	Fluid 250mm head (mm)
10	360	1200	900	2500
20	950	2600	1900	3000
30	1500	3000	3000	3000+
40	2200	3000+	3000+	3000+
50	3000	3000+	3000+	3000+

Expansion and Height Change Properties

Conbextra HF demonstrates controlled expansion characteristics critical for non-shrink performance:

Change in Height at Early Age (Final Setting Time): +0.40% (ASTM C827:2016)

Height Change of Hardened Grout (Moist Cure):

• 1 day: +0.02%
• 3 days: +0.06%
• 14 days: +0.10%
• 28 days: +0.11%
• 28 days + 28 days in air: +0.11%

Mixing Requirements

A forced-action mixer is essential for optimal results. The grout should be mixed for 3 to 5 minutes at slow speed (400/500 rpm) in a suitably sized drum using appropriate equipment such as a 140mm helical mixing paddle fitted to a heavy-duty 1600W mixer.

Mixing procedure: Accurately measure the selected water content into the mixing bucket. While mixing, slowly add the total contents of the Conbextra HF bag and mix continuously for 3 to 5 minutes, ensuring a smooth, even consistency is achieved. Always add the powder to the water.

Key Entities and Related Information

Material Classification

• Grout Type: Cementitious, non-shrink
• Dual Shrinkage Compensation: Class A (plastic state) and Class C (hardened state) expansion systems
• Product Form: Ready-to-use dry powder

Packaging and Storage

• Bag Size: 20kg moisture-resistant plastic bags
• Shelf Life: 36 months from date of manufacture when stored properly in original, unopened bags

Application Methods

Conbextra HF supports multiple placement techniques:

• Free-flowing precision grouting – Primary application method for critical installations
• Pumped grouting – Suitable for large volumes due to excellent flow characteristics
• Gravity pouring – Effective when access permits

Performance Standards Verification

Conbextra HF has been tested and verified to meet the stringent requirements of ASTM C1107:2020, which establishes comprehensive testing methodologies and acceptance criteria for non-shrink grout materials. This compliance ensures that the product delivers reliable dimensional stability and consistent expansion characteristics across various construction applications.

References

• [1] Fosroc_Conbextra_HF_TDS.pdf